Wood burning stove

ABSTRACT

A wood stove defining an upper combustion chamber and a lower fire box having two inwardly and downwardly angulated opposed fuel chutes for gravitational feeding of fuel to the fire box for extended burning. A rectilinear air channel spaced apart from a back wall of the stove, and structurally attached thereto, provides a channel for combustion products and byproducts to pass from an upper inner portion of the stove adjacent a chimney port downwardly to the fire box to pass through the primary fire zone for more complete combustion of the combustion products and combustion byproducts to enhances heat production and reduce wasting of smoke generating particulates and vapors.

II. BACKGROUND OF INVENTION

IIA. Related Applications

There are no applications related hereto heretofore filed in this or inany foreign country.

IIB. Field of Invention

This invention relates to stoves and furnaces, and more particularly toa stove having a downdraft air feed and a fuel supply hopper.

IIC. Background and Description of Prior Art

Combustion is the rapid oxidation of fuel with the release of heat andlight. Byproducts of combustion are vapors, including partiallycombusted fuel, and carbon particulates that are wasted to theatmosphere.

Combustion occurs in two stages. First, volatile gases are liberatedfrom the fuel. Second, the volatile gases are oxidized when they areignited in the presence of oxygen. The heat released in the oxidationliberates more volatile gasses from the fuel. Ignition of the gassesleads to more oxidation which generates more heat. The process continuesso long as there is fuel and oxygen.

Oxidation only occurs when the temperature is high enough to ignite thevolatile gasses. In a stove where solid fuels are combusted,temperatures are sufficiently high to ignite the volatile gasses only ina limited area known as the primary fire zone which is the area in afire where the flame is blue in color. Above, below, and adjacent theprimary fire zone temperatures are not sufficient to ignite the volatilegasses, leading to incomplete combustion.

Incomplete combustion generates large quantities of carbon particulatesand vapors that are wasted to the atmosphere. Carbon particulates andvapors are the “building blocks” for smoke. The more particulates andvapors released, the more dense the smoke. Conversely, completecombustion of the volatile gasses generates fewer carbon particulates,fewer vapors and less smoke while increasing the efficiency of the stoveand increasing heat generation.

Complete combustion occurs when the temperature is high enough to igniteall the volatile gasses and hydrocarbons for a sufficient amount of timefor ignition and oxidation to occur. One method to increase thepercentage of combustion is to “re-burn” the combustion products bydirecting the combustion products back into the primary fire zone wherethe temperature is the highest and where ignition of the volatilegasses, vapors and carbon particulates occurs.

Air typically moves into the primary fire zone from below or laterallythereto because the heat generated by the oxidizing fuel causes gaseousexpansion in and above the primary fire zone. The rising heat and gassescreate updrafts. As the heat and gasses move upwardly a low-pressurearea is created below the fire into which air is drawn to further feedthe fire. Commonly this air enters the low-pressure area throughadjustable vents defined in a bottom portion of the stove. Adjusting theair flow into the stove by opening and closing the vents regulates therate of fuel consumption, by limiting the amount of oxygen available foroxidizing the volatile gasses.

Prior art discloses various methods and apparatus to circulate air intothe primary fire zone of a stove including electrically powered andmechanically powered fans as well as strategically positioned air vents.Unfortunately, known methods and apparatus use fresh air rather thancombustion products. Further, known methods and apparatus require movingparts and energy sources, such as electricity, which makes suchapparatus prone to break downs, operating inefficiencies, needingregular maintenance, and causing higher manufacturing costs.

My stove overcomes these drawbacks by providing a wood burning stovehaving a lower fire box, an upper inverted triangular combustion chamberand a re-burner channel communicating therebetween. One end of there-burner channel is adjacent an exhaust port in a top portion of thecombustion chamber, and the opposing end is in the fire box adjacent theprimary fire zone.

When heated combustion products rise upwardly from the primary fire zonethey cool by being removed from the fire. This cooling is accentuated bythe inverted triangular shape of the combustion chamber where the volumeinside the stove proximate to its top portion is greater than the volumeproximate to the fire box. After the somewhat cooled combustionproducts, including gasses, carbon particulates and vapors, rise intoand collect in the upper portion of the combustion chamber, thecombustion products must pass outwardly through an exhaust port whichhas an orifice smaller than the top of the stove. Alternatively, thecombustion products must pass outwardly through orifices communicatingwith the re-burner channel.

The entry orifices to the re-burner channel cause a venturi effect wherehigher pressure inside the combustion chamber forces the combustionproducts through the smaller orifices at a higher velocity. After thecombustion products pass through the orifices the venturi effectdissipates and the combustion products cool further because pressure andvelocity have decreased. The cooled combustion products move downwardlythrough the re-burner channel as additional heated and fast-movingcombustion products enter the re-burner channel at its top portion, andas the fire the fire box sucks air from below to continue oxidizing thevolatile gasses liberated from the solid fuel. The downwardly movingcombustion products in the re-burner channel exit the re-burner channelat its bottom end and re-enter the fire box adjacent below the primaryfire zone and are drawn into the primary fire zone where temperaturesare the highest and ignition and oxidation is ongoing. The result is anadditional portion of the combustion products are combusted by passingthrough the primary fire zone more than once which decreases the amountof these materials being wasted to the atmosphere. The process alsorecycles previously heated air which increases heat generation.

My stove is small, carries a fuel supply for extended burning time,generates high heat and re-burns air and combustion products to morecompletely combust fuel providing a more efficient, long burning, nearsmokeless and high heat generating wood burning stove.

The configuration of my stove with its inverted truncated triangularshape with gravity powered fuel chutes opening to the top and theabsence of fuel doors that pivot outwardly from the stove also make mystove more user friendly for persons who may have physical disabilities,such as being confined in a wheelchair. The absence of an outwardlyswinging fuel door allows persons in wheel chairs to approach the stove,fuel the fire and tend the fire without having to navigate around a hotopen door, and risk burning fuel falling out of the stove.

My invention does not reside in any one of the identified featuresindividually but rather in the synergistic combination of all of itsstructures, which give rise to the functions necessarily flowingtherefrom as hereinafter specified and claimed.

III. SUMMARY

My wood stove generally provides a peripherally defined stove bodyhaving a lower fire box and an upper inverted triangular combustionchamber with two inwardly and downwardly angulated fuel chutes therein.A re-burner channel communicates between an upper portion of thecombustion chamber and the fire box and moves combustion products fromthe combustion chamber back to the fire box for re-burning.

In providing such an apparatus it is:

a principal object to provide a wood burning stove having a channelcommunicating between an upper combustion chamber and a lower fire boxfor combustion products to move downwardly from the combustion chamberback into the fire box for re-burning.

a further object to provide such a stove having a gravity powered feedsystem for extended burning time that requires infrequent operatorattention.

a further object to provide such a stove that wastes less incompletelyburned combustion products to the atmosphere.

a further object to provide such a stove that is more fuel efficient.

a still further object to provide such a stove that is handicap operableand handicap accessible.

a still further object to provide such a stove that is of new and noveldesign, of a rugged and durable nature, of simple and economicmanufacture and one that is otherwise well suited to the uses andpurposes for which it is intended.

Other and further objects of my invention will appear from the followingspecification and accompanying drawings which form a part hereof. Incarrying out the objects of my invention it is to be understood that itsstructures and features are susceptible to change in design andarrangement with only one preferred and practical embodiment of the bestknown mode being illustrated in the accompanying drawings and specifiedas is required.

IV. BRIEF DESCRIPTIONS OF DRAWINGS

In the accompanying drawings which form a part hereof and wherein likenumbers refer to similar parts throughout:

FIG. 1 is an isometric back, top and left side view of my wood stove.

FIG. 2 is a reduced orthographic back view of the stove of FIG. 1.

FIG. 3 is a reduced orthographic front view of the stove of FIG. 1.

FIG. 4 is an orthographic left side view of the stove of FIG. 1.

FIG. 5 is an orthographic right side view of the stove of FIG. 1.

FIG. 6 is an orthographic top view of the stove of FIG. 1 with the fuelchute covers removed.

FIG. 7 is an isometric partial cutaway back, top and left side view ofthe stove of FIG. 1.

FIG. 8 is an orthographic left side cross section view of the stove ofFIG. 1, taken on line 8-8 thereon, showing the interior of the stove andthe circulation of combustion products through the air re-burnerchannel.

FIG. 9 is an orthographic front cross section view of the stove of FIG.1, taken on line 9-9 thereon, showing the fuel chutes, the infloworifices to the re-burner channel and the rectilinear opening at thebottom of the re-burner channel within the fire box

V. DESCRIPTION OF PREFERRED EMBODIMENT

As used herein, the term “bottom”, its derivatives, and grammaticalequivalents refers to the portion of my stove that is closest to asupporting surface such as a floor. The term “top”, its derivatives, andgrammatical equivalents refers to the portion of the stove that is mostdistant from the supporting surface. The term “outer”, its derivatives,and grammatical equivalents refers to a side portion of the stove asopposed to the laterally medial portion of the stove.

My wood stove is constructed of sheet steel with welded seams andprovides a peripherally defined stove body 10 formed by a lowerrectilinear fire box 11, an upper combustion chamber 12 having aninverted truncated triangle shape with two angulated fuel chutes 28, 35therein, and a re-burner channel 13 communicating between the combustionchamber 12 and the fire box 11.

The fire box 11 has a front 15, a back 16, a bottom 19 and two sides 17,18 that are welded together at adjoining edge portions forming an opentop rectilinear cavity. Two vertically spaced apart hinges 23 arestructurally carried by side 17 of the fire box 11 at an edge portionadjacent the front 15. The hinges 23 carry an opening and closing ashdoor 22 that provides access to the fire box 11 through an orifice (notshown) defined in side 17. A known fuel grate 60 is carried in the firebox 11 spacedly above the bottom 19 to support solid fuel thereon.Configuration of the grate 60 allows ashes, solid combustion productsand the like to fall therethrough. A latch 24 is carried by the ash door22 opposite the hinges 23 to lock the ash door 22 in a closed position.

Plural spacedly arrayed air vents 20, each having an operator adjustablecover (not shown), are defined in the stove body 10 to control theinflow of air and plural spacedly arrayed stove feet 21 are structurallycarried by and depend from the bottom 19 to support the stove body 10above the supporting surface (not shown).

As shown in FIGS. 2 and 3, the combustion chamber 12 has an invertedtruncated triangle shape and is peripherally defined by a front 25, aback 26, a top 27, a first outer side 29 and a second outer side 36. Theouter sides 29, 36 are structurally attached, preferably by welding, tothe front 25 and back 26 at adjoining edge portions so that the front 25is spaced apart from the back 26. A planar top 27 defining rectilinearfeed port 32, 39 in each lateral edge portion is structurally attachedto upper most edges of the front 25, back 26 and outer sides 29, 36.

As shown in FIGS. 7 and 9, the outer sides 29, 36 also function asinwardly and downwardly angulated bottoms to fuel chutes 28, 35 whileinner chute sides 30, 37 function as tops to each fuel chute 28, 35.Front and back edge portions of each inner chute side 30, 37 arestructurally attached to inner surfaces of the front 25 and back 26peripherally forming the fuel chutes 28, each of which defines a channelextending therethrough.

The inner chute sides 30, 37 are structurally attached at upper endedges to the underside of the top 27 while the lower ends are spacedlyapart from one another forming a gap 59 therebetween spacedly above thefire box 11. The angulation of each fuel chute 28, 35, relative tovertical, is sufficiently steep to overcome frictional resistancebetween the inner surfaces of the fuel chutes 28, 35 and any wood fuelsliding downwardly therein (not shown) so that the wood fuel moves underthe force of gravity into the fire box 11.

Feed ports 32, 39 defined in the lateral edge portions of the top 27communicate with upper end portions of the fuel chutes 28, 35respectively while lower end portions of each feed chute 28, 35 arewithin the combustion chamber 12 spacedly above the fire box 11 (FIG.9).

A recessed lip 58 around the periphery of each feed port 31, 39positionally maintains a feed chute cover 33 that is used to cover thefeed ports 31, 39 and provide a generally airtight seal. A cover handle34 facilitates user positioning of the cover 33.

A chimney port 14 is defined in the top 27 generally medially betweenthe inner chute sides 30, 37 and provides an orifice for combustionproducts to exit the stove for wasting to the atmosphere.

Two re-burner channel inflow orifices 52 (FIG. 9) are defined in theback 26 of the combustion chamber 12 adjacent the top 27 and adjacenteach inner chute side 30, 37.

A pivoting gate damper 40 is carried on axle 41 extending through andacross medial chamber 61 adjacent the chimney port 14. A handle 42communicates with the axle 41 allowing an operator to manipulate thegate damper 40 inside the medial chamber 61 to regulate air flow andfuel consumption. A counterbalance weight 43 is slidably carried on thehandle 42 so that the damper 40 may be positionally maintained asdesired by positioning the weight 43 closer to, or away from, the axle41 and fixing its position with a set screw. (not shown).

The combustion chamber 12 and fire box 11 are structurally attached toone another, preferably by welding, along adjoining edges of the fronts25, 15 and adjoining edges of the sides 29, 17 and 36, 18 respectively.Because the front 15 to back 16 dimension of the fire box 11 is greaterthan the front 25 to back 26 dimension of the combustion chamber 12, theback 26 of the combustion chamber 12 is not directly connected to theback 16 of the fire box 11, leaving a rectilinear opening (not shown)therebetween. Further, the top to bottom height of the back 26 of thecombustion chamber 12 is greater than the top to bottom height of thefront 25 of the combustion chamber 12. This difference in dimensioncauses bottom end portion 26 a of the back 26 to extend downwardly intothe fire box 11. (FIG. 8). The lateral edges (not shown) of the bottomend portion 26 a of the back 26 are structurally attached to the innersurfaces (not shown) of the sides 17, 18 of the fire box 11 forming arectilinear channel 47 a between sides 17, 18 and between the back 26and the back 16 of the firebox 11.

The re-burner channel 13 is formed from a rectilinear back plate 44having a top edge, a bottom edge and opposed side edges and two elongaterectilinear side plates 45, 46. Each side plate 45, 46 is structurallyattached to one side edge of the back plate 44 along adjoining edgeportions to extend perpendicularly therefrom.

Edges of each side plate 45, 46 opposite the back plate 44 arestructurally fastened to the back 26 of the combustion chamber 12forming a rectilinear channel 47 b between the back 26 of the combustionchamber 12 and the back plate 44 and medially between the two sideplates 45, 46. As shown in FIGS. 2, 4 and 5, the top edge of the backplate 44 and upper end portions of the side plates 45, 46 arestructurally attached to the top 27 forming an airtight sealtherebetween. The side plates 45, 46 are laterally outward the re-burnerinflow orifices 52 so that both re-burner inflow orifices 52 communicatewith the re-burner channel 47 b. Bottom edge of the back plate 44 isstructurally attached to top edge of the back 16 of the fire box 11 sothat rectilinear channel 47 b communicates with channel 47 a between thelower end portion 26 a of the back 26 and the back 16 of the fire box11.

Caps 55 at the upper back corners of the fire box 11 are structurallyattached to the fire box 11, to one side plate 45, 46 and to the back 26of the combustion chamber 12 providing an airtight seal between the firebox 11, the combustion chamber 12 and the re-burner channel 13.

Having described the structure of my wood stove, its operation may beunderstood.

The stove is installed in compliance with codes and ordinances thatregulate wood burning stove safety.

The fuel chute covers 33 are removed from the feed ports 32, 39 definedin the top 27 and pieces of wood fuel (not shown) are insertedelongately into each fuel chute 28, 35. The configuration of the fuelchutes 28, keep the fuel (preferably elongate pieces of wood) inelongate alignment. The bottom end portions of the pieces of fuel extenddownwardly into the fire box 11 in an angulated orientation. After thefuel chutes 28, 35 are loaded with a supply of fuel, the covers 33 arereplaced on the feed ports 32, 39 and aligned so that the covers 33 fitflush upon the recessed lip 58. The damper handle 42 is positioned sothat the damper 40 is open and the set screw (not shown) is secured tokeep the damper 40 open.

The ash door 22 and the spacedly arrayed air vents 20 are opened. Asupply kindling, or other fire starter (not shown), is placed on thefuel grate 60 in the fire box 11 adjacent to and below the bottom endportions of the fuel extending downwardly from the fuel chutes 28, 35.

Depending upon environmental conditions, such as the temperature andhumidity, it may be necessary for the operator to establish an air drawwithin the stove so that the stove operates properly. Igniting a pieceof fast burning material and placing it in medial chamber 61 willtypically initiate an air draft. As the fast burning material burns, airin the stove is heated, causing it to expand and move upwardly throughthe combustion chamber 12 and exit out through the chimney port 14. Asthe heated air within the stove moves upwardly, cool air enters thestove through the air vents 20 and through the ash door 22 establishingthe air draw.

The supply of fine kindling or other fire starter is ignited with knownmeans. The ash door 22 is closed and secured with the latch 24. The airdraft, previously started within the stove provides oxygen to the newlyignited fire by drawing air through the air vents 20 which are open. Theburning kindling heats the bottom end portions of the fuel extendingangularly downwardly from the fuel chutes 28, 35, liberating volatilegases from the wood fuel. The volatile gases ignite and oxidize in thefire box 11 above the fuel grate 60. The oxidizing releases more heatwhich liberates more gases and the process continues, consuming the woodfuel. As the lower end portions of the wood fuel are consumed by thefire, gravity pulls the upper portions of the fuel down the feed chutes28, 35 and into the fire box 11 to be burned. Gravity powers theself-feeding nature of the stove.

Expanding gases and heat generated by the oxidizing gases rise upwardlyagainst the underside of the top 27. As the combustion continues, moreheat and expanding gases, including vapors and carbon particulates riseupwardly into the medial chamber 61 increasing the pressure therein. Aportion of the vapors, expanding gases and heat pass through the chimneyport 14 and are wasted to the atmosphere. Because the chimney port 14 isareally smaller than the upper area of the medial chamber 61, pressureincreases in the area adjacent and about the chimney port 14. Gaseousfriction between the underside of the top 27 defining the chimney port14 and the combustion products slows the passage of combustion productsthrough the chimney port 14 which further increases the pressure in themedial chamber 61. The increased pressure forces some of the combustionproducts, including vapors, carbon particulates, heat and gases throughthe re-burner inflow orifices 52 into the re-burner channel 13.

The areally smaller re-burner inflow orifices 52 cause a venturi effectwhere higher pressure inside the medial chamber 61 forces the combustionproducts through the smaller re-burner inflow orifices 52 at a highervelocity. After the combustion products pass through the areally smallerre-burner inflow orifices 52 the venturi effect dissipates and thecombustion products cool because pressure and velocity have decreased.The cooled combustion products move downwardly through rectilinearchannels 47 b, 47 a which in combination form the re-burner channel 13as additional combustion products enter channel 47 b through there-burner input orifices 52 at its top portion, and as the fire the firebox 11 “sucks” air from below.

Because the re-burner channel 13 has three exterior surfaces, the backplate 44, and the side plates 45, 46, that are not directly exposed tothe primary fire zone they are cooler in temperature than the fire box11 and combustion chamber 12. This causes combustion products within there-burner channel 13 to cool. As the combustion products cool theybecome more dense and move downwardly through the re-burner channel 13.

The oxidizing of the fuel in the fire box 11 draws air from allavailable sources including the air vents 20 and the re-burner channel13. When the operator restricts airflow through the air vents 20 byclosing the adjustments (not shown) thereon, the fire draws more airthrough the re-burner channel 13. The combustion products passingthrough the re-burner channel 13 contain carbon particulates, vapors andother combustion products that form smoke when released to theatmosphere.

Because the combustion products passing through the re-burner channel 13enter the fire box 11 through the rectilinear orifice 53 adjacent belowthe primary fire zone, the combustion products pass through the primaryfire zone again where they are again subjected to temperaturessufficiently high for ignition and oxidation. The result is a small butintense fire that provides more heat through substantially completecombustion of fuel, and a wood fuel stove that generates less combustionbyproducts that cause smoke.

The foregoing description of my invention is necessarily of a detailednature so that a specific embodiment of a best mode may be set forth asis required, but it is to be understood that various modifications ofdetails, and rearrangement, substitution and multiplication of parts maybe resorted to without departing from its spirit, essence or scope.

Having thusly described my invention, what I desire to protect byLetters Patent, and

1. a stove for burning solid fuel comprising in combination: a bodyhaving a combustion chamber at an upper end portion structurallyconnected to and communicating with a fire box at a lower end portion,the body defining a medial chamber; the combustion chamber having afront, a back, a top and opposing sides, the top defining chimney portfor wasting combustion products; the fire box defining at least one airvent and an orifice having a door; two inwardly and downwardly angulatedopposing fuel chutes in the combustion chamber, each fuel chute havingan upper end portion communicating with a feed port defined in the top,a lower end portion in the medial chamber spacedly above the fire box,and defining a medial channel extending therethrough for feeding fuel tothe fire box; a re-burner channel structurally carried by the back ofthe combustion chamber, the re-burner channel defining a rectilinearchannel communicating between the combustion chamber and the fire boxfor passage of combustion products and byproducts therethrough; and arecirculation in-flow orifice defined in the back of the combustionchamber proximate to the top and communicating with the rectilinearchannel of the re-burner channel for combustion products and byproductsto pass therethrough.
 2. The solid fuel stove of claim 1 wherein: thecombustion chamber has an inverted truncated pyramid shape, and the firebox is rectilinear having a front, a back, opposing sides and a bottomthat are structurally interconnected.
 3. The solid fuel stove of claim 1wherein: the inward and downwardly angulation of the opposing fuelchutes provides gravity powered feeding of solid fuel into the medialchamber and the fire box.
 4. The solid fuel stove of claim 1 wherein:the re-burner channel has a back plate and two structurally attachedside plates, the back plate extending parallel to the back of thecombustion chamber and communicating between the top of the combustionchamber and the fire box, the two side plates structurally communicatingbetween the back plate and the back of the combustion chamber topositionally maintain the back plate spaced apart from the back of thecombustion chamber.
 5. The solid fuel stove of claim 1 wherein: the backof the combustion chamber extends downwardly inside the fire boxspacedly below the bottom end portions of the fuel chutes forming arectilinear passage between the back of the combustion chamber and aback portion of the fire box.
 6. The solid fuel stove of claim 1 furthercomprising: fuel chute covers for the feed ports defined in the top ofthe combustion chamber to seal the top end portions of the fuel chutesand prevent escape of combustion products and byproducts therethrough.